Re: Michael's ArchLinux Installation

["Kerry Hoath" <kerry@gotss.net>]

Ok lvm does allow more flexibility however there are some limits.
You can use just ramsize for swap, so 2gb would be enough and this would let 
you suspend to disk.

You can resize partitions with lvm however you need to resize the underlying 
filesystem first. You can't resize a mounted filesystem so resizing the root 
file system won't happen unless you boot from a live cd.
Usually what happens is you have a /boot partition and then the rest of the 
system loads off logical volumes. To do this however you need an initial 
ramdisk and lvm built into that initial ramdisk image. This is something i'm 
sure arch linux has.

I often actually set up /boot with say 100 megabytes, then a small root fs 
then the rest of the stuff on logical volumes.
To change the size of partitions you need to reduce the size of the file 
system then reduce the number of logical extents in the file system. not 
sure if there are tools to do this easily.

I think you can grow reiserfs when it is mounted but shrinking it requires 
an unmount.
xfs can only grow.
ext4 I believe needs to be unnmounted for resizing.

If diskspace is tight then perhaps doing without lvm would save you 
complexity.
the smallest disk I have in a server is 60 gig so space is not an issue 
here.
I don't usually use lvm on the virtual machines which are 2 gig in size, 
they don't need the complexity.

As to the comment on swap, I don't see a lot of stuff swapped out but if 
there is no swap then swapping is not an option.
Yes the system can swap to lvm although note that you need support in the 
initrd for the s2disk technology either the kernel stuff or tuxonice.
Regards, Kerry.

----- Original Message ----- 
From: "Michael Whapples" <mwhapples@aim.com>
To: "Speakup is a screen review system for Linux." <speakup@braille.uwo.ca>
Sent: Monday, April 26, 2010 8:43 PM
Subject: Re: Michael's ArchLinux Installation


> Thanks for the information. I did sort of know about the suspend to disk 
> advantage.
>
> I do have a question. As my reason for using swap files for swap space is 
> to do with having 2GB of RAM and so using the RAM times two rule for swap 
> means 4GB which is more than I think my laptop's HD wants to take 
> permanently (I mean it would restrict the other partitions more than I 
> would want to go). Now I have heard people mention about LVM allowing more 
> dynamic allocation of disk space, how possible are the following and how 
> safe are they:
>
> * To expand and shrink volumes with data on (eg. an ext4 partition holding 
> the main system)?
> * Suspend to disk, does it work if swap is a volume in LVM?
> * Is there any issues with using swap in a volume?
> * What is the options for installing grub when using LVM? Remember my 
> preference has been to install it to the partition boot sector.
>
> Thanks for any answers.
>
> Michael Whapples
> On 01/-10/-28163 08:59 PM, Jason White wrote:
>> "Kerry Hoath"<kerry@gotss.net>  writes:
>>
>>
>>> There are advantages to having a swap partition.
>>> Firstly, accessing a partition directly for virtual memory bypasses
>>> file system overhead. You can just read/write pages to absolute
>>> sectors on the partition.
>>>
>> True, although I have read claims that under modern Linux kernels, it is
>> no longer the case that swap partitions give higher performance than
>> swap files. Regrettably I can't remember the details, but I assume that
>> since space for the swap files is pre-allocated, the kernel now keeps
>> track of where the sectors are on the device so that it doesn't have to
>> invoke the file system when writing to the swap space.
>>
>> The other advantages mentioned are uncontroversially correct, though, as
>> far as I know.
>>
>>
>>
>>
>
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